A capacitance type sensor is generally used for converting into an electric signal the magnitude and direction of a force applied by an operator. For example, in an input device for a computer, a capacitance type sensor for inputting a multidimensional operation is incorporated as a so-called joystick.
With the capacitance type sensor, an operation quantity having a predetermined dynamic range can be input as the magnitude of a force applied by the operator. In addition, such a capacitance type sensor is also used as a two- or three-dimensional sensor capable of resolving into each dimensional component an applied force to be detected. In particular, capacitance type force sensors in which a capacitance element is formed between two electrodes to detect a force on the basis of a change in capacitance value caused by a change in the distance between the electrodes, have been put into practical use in various fields because they have a merit that the construction can be simplified to intend to reduce the cost.
In a capacitance type sensor, fixed electrodes on the X-axis, fixed electrodes on the Y-axis, and a fixed electrode on the Z-axis surrounded by the X- and Y-axial fixed electrodes, cooperate with a movable electrode to form variable capacitance elements, for example, see Patent document 1. In the capacitance type sensor, for example, when an X-axial force Fx is applied to an operation portion, the distance between a fixed electrode on the X-axis and the movable electrode is decreased to increase the capacitance value of the capacitance element formed by the electrodes. Therefore, by detecting the change in the capacitance value of the capacitance element, an X-axial signal corresponding to the X-axial force Fx can be output.
Paten Document 1: Japanese Patent Unexamined Publication No. 2001-91382